Booster Idea Need Guideance

[rocket8810]

So I have this crazy idea of trying to build a one knob hybrid booster/overdrive, with two transistors (one JFET, one germanium), for bass. I got the idea while looking at the vero for the AMZ Mini-Booster, cause I know it's fairly clean sounding normally, but I figure I can get a little bit of grit, warmth, and color from the incorporation of a germanium. The reason I'm thinking to have a 2 stage booster is that the first stage (JFET) would drive the second (germanium), so the JFET would be a nice and relatively clean, while the germanium would add the color and warmth that I'm looking for. I was thinking that the single knob would be sort of a master volume, that can organically drive the germanium stage. But, to control the overall gain I want to add a trimmer so that I can just set it and forget it.

I have a few questions:
One, what would be a good circuit to use as a jumping off point? Second, is how can I replace a JFET with a germanium transistor. Third, would it be better to use germanium clipping diodes? If so, how? Lastly, in general what is the best way to add color to a circuit?

I've been messing around with a lot of the pedals pre-made and making my own variations for guitars with good results, but I'm trying to do more to make some that are more of my own, so I'm trying to learn as much as I can. Thanks for any help in advance guys.

[Gus]

Search this forum and the web for "guitar booster" and other strings like that.
Have you looked at the beginner project or any of the other boosters you can find at this site or other sites?

[midwayfair]

The mini booster uses one transistor for DC gain and one for the audio gain. They aren't cascading into one another, and the DC gain transistor has far less of an effect on the sound. You really don't get a lot of 'transistor sound' out of either to tell the truth  -- that sort of stuff doesn't really rear its head on clean tones.

But if you use a BJT in the audio path transistor, you'll get a lot more noise and a ton of harsh treble. If you use a germanium, you'll get so much noise it'll be almost unusable.

If you want to hear what a my amp sounds like with a germanium transistor, the first version of my clipper ship overdrive used one in the my amp half of that circuit (and that was a mistake). I compare the noise between the ge and fet in the demo on my webpage.

I've seen other circuits use but my amps, but they always seem to have a lot more noise.

[lopsided]

Yes, you can not just change one.transistor of the mini booster to be germanium. But maybe try to look for the fetzer valve at runoffgroove as an one stage jfet building block and put it  in front of a geanium booster such as the rangemaster.

[R.G.]

I figure I can get a little bit of grit, warmth, and color from the incorporation of a germanium.

Sadly, it is not true that you can make a circuit sound great (or even better, however you define those words) by rubbing germanium on it. Germanium transistors are just circuit components. The circuit may have a sound, but germanium transistors do not. The total circuit is what matters - except in advertising, where people will buy stuff just because it says that there's germanium inside, much like those intel stickers that used to say "intel inside".

[rocket8810]

Thanks R.G. I'm actually glad to have you respond, cause I'm actually just starting to go through all the information on your site. I understand that Germanium is not some magical part that makes something sound amazing. From what I've read and understand about the difference between Silicon and Germanium is that germanium clips earlier and produces a soft warm clipping, where as Silicon clips later and is a little harsher so speak. I know that with diodes, like on the Pharoh Fuzz from Black Arts Toneworks, and thought that the same was with transistors too. I found something similar to what I was thinking, but cant find any schematic to help me with my design. Wren and Cuff makes the phat phuk b for bass. I found this which he explains how the circuit works, which is similar to how I was thinking I wanted this pedal to work, and what I want it to do it.

.

And I found a gut shot of the phat phuk b too.



As far as changing one transistor to another, I 'm just trying to figure out how you can use 2 different types of transistors in one circuit, like the crimson drive by earthquaker, which seems to be some sort of JFET buffer, with a germanium rangemaster, and I think that transistor is PNP, while the JFET is NPN. Which really confuses me because PNP transistors can't be powered by the same power supply as NPN devices because of the difference in polarity, so that really confuses me. Also, I didn't know if a circuit is designed for a JFET or BJT if it is possible to change the circuit work with the other, ie a circuit that contains BJTs replaced with JFETs.

I have looked at many projects here and other places, and have already been making changes to some to work with bass, but I still want to add a little warmth and grit to the signal too, which is not on here. I also can not figure out how to have the one knob control both the overall output volume and grit, which is why I was thinking that the booster drives the second circuit. Hopefully the video from Wren and Cuff better explains what I'm trying to.
I'm still learning a lot of the intricacies of how effect circuits work, other than the basics I already have from other circuits I've worked with. I have not undertaken something like this before where I'm really trying to do more designing of a whole pedal rather than taking one pre-existing circuit and make changes to it. Like I have in my head a sound, and what I want the pedal to do, but not sure how to go about it, if that makes any sense. I know you guys have a lot more experience and knowledge then me, and looking for guidance so that I can get better and eventually pay it forward. I really appreciate the help so far, and hope you guys can further help me reach my goal.

[smallbearelec]

I just finished this article:

https://www.smallbearelec.com/HowTos/BeginnerArticle/BeginnerDos.htm

and some of it applies to your situation. Slow down a little, learn how One stage really works, and go on from there to adding and tweaking to get to what you want.

Regards
SD

[mistahead]

Get cheap parts, build lots of single stage boosters with transistor sockets, trim pots... BREADBOARD!!!

Swap the Ge for some Si in known good boosters, play around with lots of single stage boosters, then cascade them into each other...

But yeah - learn from the bottom up, I didn't - still haven't... not a pro lol.

[rocket8810]

Thanks for the help so far guys, I've been doing a ton or reading and research and I've made a lot of headway. Thanks to Steve I've been working on modifying his Ursa Minor, which will be the second stage Ge booster and it's almost where I want it. I'm going to start working with some JFET boosters that are know for being "clean," like the SHO, Lovepedal Delux Sixty, or possibly modifying the Escobedo Duende JFET, but I'm not yet sure how to remove the volume pot and add an input cap. I really want to go JFET as from what I've read they were made to emulate some of the characteristics of tubes. If I understand correctly J201's are similar in sounds to triodes, and bs170's are similar in sound to pentodes, but not sure which way to go. The problem is I want the first stage to add clarity to notes and a tube-like warmth, so it can open up the sound like a "tone enhancer" to thicken and sweeten the sound. Kinda hard to explain what I'm hearing in my head, lol. Any suggestions?

Keep in mind that what ever is used as the first stage will loose their volume pot, as it's going to have a voltage divider volume control at the end of the circuit after it pushes the Ge stage.

[Thecomedian]

I figure I can get a little bit of grit, warmth, and color from the incorporation of a germanium.

Sadly, it is not true that you can make a circuit sound great (or even better, however you define those words) by rubbing germanium on it. Germanium transistors are just circuit components. The circuit may have a sound, but germanium transistors do not. The total circuit is what matters - except in advertising, where people will buy stuff just because it says that there's germanium inside, much like those intel stickers that used to say "intel inside".

I thought germanium diodes smoothed clipping, without going into the details of capacitance and leakage currents of Ge PN junctions.

for wonderers on the subject, like myself, some possible resources.
http://www.seymourduncan.com/tonefiend/diy/the-germanium-mystique/
http://music.stackexchange.com/questions/1069/silicon-vs-germanium-fuzz
http://www.harmonycentral.com/t5/DIY-Do-It-Yourself/Do-germanium-diodes-and-transistors-just-sound-better/td-p/6159849
http://www.youtube.com/watch?v=mq6dl289u0o

[Mark Hammer]

My wife and I stayed with Steve Daniels and his wife Judy last week.  Steve was anxious for me to try out the Oh My Darlington Sziklai Rangemaster, that uses a pair of low gain GE transistors (the plentiful and easy/cheap-to-get kind) in Darlington configuration.

At first blush, I have to say, I wasn't crazy about it.  But admittedly, I was unfamiliar with the guitar (Guild Bluesbird) and amp (Peavey Classic 30), and couldn't tell what the pedal, amp, or guitar were contributing.  And since it was set up in the spare bedroom, and they live in a co-op, I was reticent to turn up and rock out.  We took the pedal to Matt Umanov's the next day, and tried it out with a Telecaster and Tremolux, and I was very pleasantly surprised.  When a Rangemaster works well, it doesn't "fuzz" so much as "blur"; sort of the audio equivalent of jiggling the camera just a little when you take the picture.

In any event, Steve's design - visible here: https://www.smallbearelec.com/Projects/OhMyDarling/OhMyDarling.htm - is clever, inexpensive (if you have low-gain GEs hanging around), and sounds decent.  Worth exploring.

[Mark Hammer]

I thought germanium diodes smoothed clipping, without going into the details of capacitance and leakage currents of Ge PN junctions.

Different diode types exist for a reason, and DO have different properties.  The broader question is whether those different properties all pertain to the world of the first 6000hz of the audio spectrum, or tend to be relegated to things like switching at 100khz, and so on, and only really show up there.  Even IF a diode type has a different "knee" for content at 4khz, the first-order harmonic of that (8khz) will generally be attenuated by the limitations of the speaker.

My own take (and I'm open to persuasion) is that, for our purposes here, the most salient properties of how diode types react to the signals we try and process with them, are pretty much confined to forward voltage, and just about everything we attribute to them stems from that.  That's not insignificant, but it is pretty straightforward, and easy to design around without delving into obscure hypothesized qualities.

I'm sure copper, silver, nickel, aluminum, and tin all have unique properties, but bite down hard on a penny, a nickel, a quarter, or coin in almost any currency, and you'll chip a tooth; i.e., in that specific circumstance all those different metals end up having the same net effect.  Same thing with diodes.

[Thecomedian]

copper and silver are softer, so they'll squish some before you chip that tooth, so maybe your analogy works perfectly well defining Ge vs Si to Copper/Silver vs nickel/tin.

Anyway, leakage current and capacitance are the things I think the different junctions of Ge or Si are likely the cause of different sounds.